How to make private messages on node js socket.io?

Question

Node.js

How to make private messages on node js socket.io?
There is a server, there is an authorization and a chat. Authorization is related to the chat.
Question: How is it not a general chat, but a private one?!?!? I didn't find anything on the Internet.
If possible, please provide some simple code or explain how it works.
I know how to send a message to a specific socket, by socket.id, but I don’t know how to use it and I don’t understand at all what to do with it, how to get it from the client and forward the message to him by its id. Help.

Answer 1

From the client side, pass a jwt token or a cookie (session). On the side of the node, write a middleware that, at the time of connection, will process this data and record the client.
For example, like this:

const io = socket();

io.use(async (socket, next) => {
  try {
    const { token } = socket.handshake.query;
    const data = await verify(token);
    socket.request.user = data;
    return next();
  } catch (err) {
    // ignore
    return next();
  }
})

Now you have user data in the connection object and you can send a message to a specific user by finding his connection.

Answer 2

The easiest way to learn when you already know the basics is by studying open source projects
Easier:
Let's Chat sdelements.github.io/lets-chat
node-chat https://github.com/IgorAntun/node-chat
Harder:
Rocket Chat https://rocket.chat ( https://github.com/RocketChat)
+ Socket.io itself has a good tutorial as far as I remember and Feathers.js (realtime framework based on Express)